Vacuum control for carburetor power enrichment apparatus

ABSTRACT

A solenoid valve is normally opened to bleed a part of the engine vacuum applied to operate the power enrichment system of an internal combustion engine carburetor. A transmission controlled switch closes the solenoid valve when the transmission shifts to a high drive ratio from a lower drive ratio. Since the power system varies the flow of enriched fuel inversely with engine vacuum, closure of the valve delays the commencement of fuel enrichment until the engine vacuum falls below a level lower than that at which enrichment is normally commenced with the valve open.

United States Patent [191 Price [4 1 Feb. 5, 1974 VACUUM CONTROL FORCARBURETOR POWER ENRICHMENT APPARATUS [75] Inventor: Robert T. Price,Berkley, Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Mar. 15, 1972 [21] Appl. No: 234,897

[52] US. Cl. 74/859, 123/119 R [51] Int. Cl. B60k 21/00, F02b33/00,,F02m 7/00 [58] Field of Search 123/11-9 R, 127-, 106; 74/859,

[56] References Cited UNITED STATES PATENTS 2,473,762 6/1949 Mallory123/106 3,685,502 8/1972 Oberdorfer 123/119 R 3,691,873 9/1972 Lombardet a1. 74/860 X 2,362,655 11/1944 Mallory.. 74/860 3,349,644 1 10/1967Gish 74/860 3,587,651 6/1971 McCollough.... 3,696,798 10/1972 Bishop etal. 123/119 R X Primary ExaminerAllan D. l-lerrmann Assistant ExaminerP. S. Lall Attorney, Agent, or FirmR. L. Phillips [57] ABSTRACT Asolenoid valve is normally opened to bleed a part of the engine vacuumapplied to operate the power enrichment system of an internal combustionengine carburetor. A transmission controlled switch closes the solenoidvalve when the transmission shifts to a high drive ratio from a lowerdrive ratio. Since the power system varies the flow of enriched fuelinversely with engine vacuum, closure of the valve delays thecommencement of fuel enrichment until the engine vacuum falls below alevel lower than that at which enrichment is normally commenced with thevalve open.

3 Claims, 4 Drawing Figures IGNITION TIMING SYSTEM $1 Patented Feb. 5,1974 3,789,702

lGNlTION TIMING SYSTEM P BLEED- 17 CLOSED F I6 W5 -l4 LL|3 BLEED oPENE|2 I I 1 a A 4567s9lo|| |2|3 ENGINE VACUUM H3."

|3 BLEED CLOSED 9"H g1.2 fii 5 11 2 BLEEDJ 8 OPEN 7H9 9 a PP D 8 LL 7 5060 76 ab VEHICLE SPEED MPH VACUUM CONTROL FOR CARBURETOR POWERENRICHMENT APPARATUS ered. However, while lowering the N/V ratio usuallyimproves fuel economy, it has been found that significant improvementsin fuel economy are not readily obtainable as the N/V ratios drop to 30.

The present invention recognizes that one reason for this loss of extraeconomy is that, in comparable driving conditions, the engine vacuum isnormally reduced as the N/V ratio is lowered and that the powerenrichment system in the usual commercial carburetor, since it enrichesfuel flow with decreasing engine vacuums, is

' therefore used for a greater proportion of the time in normalmaneuvers. Such greater use of the power enrichment systems in normalcruise driving prevents the attainment or potential fuel economy thatmight otherwise be realized by lowering the N/V ratio. The presentinvention further recognizes that normal operation of the powerenrichment system may not be necessary during normal expressway orhighway driving of vehicles having low N/V ratios.

Loss of some of the potential fuel economy otherwise obtainable bylowering the N/V ratio is avoided in the present invention by a solenoidvalve that normally allows some of the engine vacuum for operating thepower enrichment system of an internal combustion engine carburetor tobleed off when the vehicle transmission is not in high gear. When thetransmission shifts to a high drive ratio, the solenoid valve is closedby a transmission controlled switch that is already available to controlthe applicationof engine vacuum to a vacuum advance unit on the enginetiming distributorto permit vacuum advanced ignition timing. Since thepower enrichment system varies the flow of enriched fuel to the engineinversely with engine vacuum, closure of the solenoid valve delays thecommencement of fuel enrichment until the engine vacuum falls below alevel lower than that'at which enrichment is normally commenced with thevalve open.

It is an object of the present invention to provide a new and improvedpower enrichment system for an internal combustion engine carburetor.

It is another object of the present invention to provide, in an internalcombustion engine carburetor having a power enrichment system forvarying the flow of enriched fuel inversely with engine vacuum, avehicle speed controlled apparatus for operating the power enrichmentsystem with more of the available engine vacuum with increasing vehiclespeeds.

ltis another object of the present invention to provide, in an internalcombustion engine combustion for varying the flow of enriched fuel tothe engine inversely with varying engine vacuums, vehicle speedcontrolled apparatus for delaying the commencement of enriched fuel flowuntil the engine vacuum falls below a level 2 lower than the level atwhich fuel enrichment is normally commenced.

It is another object of the present invention to provide a vehicle speedcontrolled apparatus of the foregoing type wherein ajportion of theengine vacuum otherwise available for operating the power enrichmentsystem is normally exhausted through a solenoid valve that is closed bya switch actuated by the shift of the vehicle transmission to a highdrive ratio, the higher vacuum applied to the power enrichment systemwith the valve closed in high gear reducing the flow of enriched fueland improving fuel economy.

It is another object of the present invention to provide a powerenrichment system of the foregoing type wherein the switch for closingthe solenoid valve also controls a vacuum advanced ignition timingsystem.

These and other objects and features of the present invention willbecome more apparent with reference to the following description takenin conjunction with the accompanying drawings wherein:

FIG. 1 is a cross-section of a carburetor having power enrichmentapparatus incorporating a transmission controlled vacuum bleed controlsystem provided in accordance with the present invention:

.FIG. 2 is a view showing the power enrichment apparatus of FIG. 1 ingreater detail;

, FIG. 3shows the air/fuel versus engine vacuum characteristics obtainedwhen the vacuum bleed of the carburetor in FIGS. 1 and 2 is open in highgear and when it is closed; and 7 FIG. 4 shows the fuel economy versusvehicle speed characteristics obtained at given engine vacuums when thecarburetor of FIGS. land 2 provides fuel to the engine of the vehiclewith the vacuum bleed open and with the bleed closed. I

With reference now to FIG. 1, there is shown partly in outline acarburetor 10 incorporating a transmission controlled vacuum bleedcontrol system 12 provided in accordance with the present invention anddescribed in further detail below. Carburetor 10 provides an air-fuelmixture to an induction passage 14 of an internal combustion engine 16under the control of a throttle valve 18. Engine 16 is connected todrive the vehicle wheels 20 and 22through an automatic transmission 24,a differential 26 and axles 28 and 30. To provide'fuel to meet thedemands of engine 16, carburetor 10 has a fuel delivery passage denotedgenerally at 32 that includes fuel metering means 34, primary fueldelivery channel 36, and an idling channel 38.

Fuel metering-means 34 further includes a valve seat 40 having a centralorifice 42 therethrough and a metering rod 44 having a tapered end 46extending through orifice 42. A power enrichment system 48 is providedto normally position tapered end 46 in orifice 42 in accordance with avarying engine vacuum communicated from induction passage 14 to a vacuumchamber 50 through a vacuum channel 52 and a flow restriction 53, thepurpose of which is described below. To increase the flow of enrichedfuel through orifice 42 as the engine vacuum in induction passage 14decreases, enrichment system 48 includes a piston 54 translatable in apiston chamber 56, one end of which communicates with vacuum chamber 50through an opening 58 in a plate 59 and the other end of which has anopening 60 for communicating with atmospheric pressure normally upstreamof metering means 34. The upper end of piston b4 as viewed in FIG. 2 hasan arm 62 extending through opening 60 for positioning and pivotablysupporting metering rod 44. A spring 64 biases the bottom of piston 54upwards from plate 59 so as to cause arm 62 to retract tapered end 46 ofmetering rod 44 out of orifice 42 and thereby increase the flow areatherethrough. As the vacuum in vacuum chamber 50 increases, the pressuredifferential between the top and bottom sides of piston 54 acts againstthe upward bias of spring 64 to translate piston 54 downwards until anadjustment rod 66 secured to the bottom of piston 54 and extendingthrough opening 58 in plate 59 abuts against one leg 68 of adjustmentclip 70 located in vacuum chamber 50. Clip 70 thus stops furtherdownward translation of piston 54 and maintains a minimum flow areathrough orifice 42 as the engine vacuums increase above a predeterminedlevel. As the engine .vacuum falls below this level, spring 64 urgespiston 54 upwards until piston arm 62 abuts roof 72 at which point rod66 determines the maximum flow area through orifice 42. The abovedescribed power system 48 may be of the conventional type in operationdescribed on page 6-60 of the 1972 Cadillac Shop Manual published by theGeneral Motors Corporation.

It has been found that as the engine 16, transmission 24 anddifferential 26 are sized to require fewer engine revolutions per mileper hour of vehicle speed, thereby lowering what is called the N/Vratio, the engine vacuum in induction passage 14 is normally reduced forcomparable driving conditions, especially under normal expressway oropen highway cruising conditions where the N/V ratio of a given vehicleis usually the lowest. Therefore, unless its normal operation isprevented under these cruise conditions, power system 48 would otherwiseprovide a flow of enriched fuel merely because of the vacuum-reducingeffect of the lowered N/V ratio and not because the operatorof thevehicle desired the increased performance normally associated with powerenrichment. Since it has also been found that adequate vehicleperformanceis obtained under these cruise conditions without any flow ofenriched fuel, fuel economy is obtained with vacuumbleed control system12 of the present invention by delaying the commencement of operation ofpower system 48 at high vehicle speeds until the engine vacuum drops toa level lower than that at which the power system 48 normally commencesoperation at lower speeds.

Since high speed operation of the vehicle is usually effected when thedrive ratio between the revolutions of output shaft 23 of transmission24 to the revolutions of input shaft 25 thereof is the highest, vacuumbleed control system apparatus 12 is activated to prevent the normaloperation of power system 48 when transmission 24 is shifted into itshigh drive ratio from a lower drive ratio. For this purpose, vacuumbleed control system 12 includes a conduit 80, one end of whichcommunicates with vacuum chamber 50 in carburetor through a flowrestriction 82, a commercially available solenoid valve 84 forexhausting the other end of conduit 80 to atmosphere, a transmissioncontrolled switch 86 mounted on and operated by transmission 24, and aconductor 88 for energizing solenoid valve 84 with power from a vehiclebattery 90. These components cooperate so that with transmission 24 in alow drive ratio, transmission controlled switch 86 is normallydeenergized and solenoid valve 84 is normally open to bleed the vacuumin vacuum chamber 50 at rates varying with the vacuum and the sizes ofrestrictions 53 and 82. When in a high drive ratio, transmission 24closes transmission controlled switch 86 to energize solenoid valve 84thereby stopping the bleed of vacuum from vacuum chamber 50 throughconduit 80.

Also connected by a conductor 92 to transmission controlled switch 86 isan ignition timing system 94 which may be of the type described in U.S.Pat. No. 3,584,521, entitled lgnition Timing Arrangement issued toRichard Tooker and James Dawson on June 15, 1971, assigned to theassignee of the present invention, and hereby incorporated herein byreference. As more fully described in the Tooker et al. patent, timingsystem 94 has a valve operated by a switch such as switch 86 forcontrolling the communication of engine vacuum to a vacuum advance uniton the vehicle ignition distributor so as to permit vacuum advancedignition timing when the transmission is in a high drive. Such advancedtiming has been found advantageous in reducing automotive exhaustemissions, unburned hydrocarbons and oxides of nitrogen. As also shownin the Tooker et al. patent, transmission controlled switch ,86 may becontrolled in accordance with vehicle speed as determined by a signalfrom a governor on the output shaft of the transmission or may becontrolled by a drive ratio shift valve in the transmission.

In normal operation of power enrichment system 48, the position ofmetering rod 44 is varied in accordance with the varying engine vacuumin induction passage 14 to vary the flow area through orifice 42 betweena minimum and a maximum. Metering rod 44 is positioned to effect theminimum flow area when the magnitude of the vacuum in vacuum chamber 50is sufficient to hold rod 66 against clip leg 68 against the upward biasof spring 64. When in this minimum flow area position, metering means 34still permits fuel to flow at a rate determined by the pressure dropbetween the substantially atmospheric pressure on the up-stream side oforifice 42 compared to the downstream pressure in either primarydelivery passage 36 when throttle valve 18 is in an open position 1 8shown dotted or in idle passage 38 when. throttle valve 18 is in an idleposition shown solid. With the throttle valve 18 open, the flow of fuelthrough metering means 34 when in the minimum flow area condition isnormally sufficient to sustain non-enriched vehicle operation underconstant loads, and with throttle valve 18 closed in its idle position,the flow of fuel through metering means 34 is normally sufficient tosustain idle operation of engine 16.

Transmission controlled switch 86 is normally open in this normaloperation of power system 48 so that solenoid valve 84 is normallydeenergized and open to bleed the vacuum in vacuum chamber 50.Restriction 53 cooperating to some extent with restriction 82 restrictsthe loss of engine vacuum available in induction passage 14 whensolenoid valve 84 is open. Restriction 82 also cooperates with spring 64to determine the level below which the engine vacuum must fall beforethe pressure differential across piston 54 is sufficient to allow spring64 to retract metering rod 44. For example, with bleed valve 84 open,the carburetor 10 and power system 48 of FIGS. 1 and 2 provide a lean oreconomy mixture until the engine vacuum is l l'inches of mercury, a fullpower or rich mixture at a vacuum of 5 inches, and a mixture halfwaybetween lean and rich at a vacuum of 8 inches, thereby also providing anair fuel ratio versus induction passage characteristic similar to thatindicated by the dotted line in FIG. 3.

The above described normal operation of power system 48 is preventedwhile also permitting vacuum advanced timing in ignition timing system94 when trans mission 24 shifts to a high drive ratio to closetransmission controlled switch 86 and there-through energize solenoidvalve 84 to cut off the bleed through conduit 80. The pressuredifferential across piston 54 is then increased by the amount of vacuumnormally bled through conduit 80 to correspondingly advance metering rod44 into orifice 42 and reduce the flow area therethrough.

As may be better understood with reference to FIG. 3, by closing thebleed to vacuum chamber 50, vacuum bleed control system 12 is operativeto lower from 11 inches of mercury to 6 inches the level of vacuumrequired in induction passage 14 for the commencement of fuelenrichment. The commencement of enriched I fuel is thus delayed untilthe engine vacuum has dropped to a level lower than that at whichenriched fuel flow would be provided with the bleed open. Such delay inthe attainment of the vacuum level required for power cut-in causes aleaner air fuel mixture to result at given levels of vacuum during thedelay. Thus, closing bleed valve 84 in carburetor 10 of FIGS. 1 and 2provides a lean or full economy mixture until the vacuum drops to 6inches and full power or rich mixture at 4 inches, as indicated by thesolid air-fuel ratio versus engine vacuum characteristic of FIG. 3.Since running on leaner mixtures normally results in fuel economy, sucheconomy may be obtained by the vacuum bleed control of the presentinvention for manifold vacuums between 4 inches and 11 inches. Forexample, a commercial passenger vehicle fitted with a four-speedoverdrive transmission provided fuel economy versus vehicle speedcharacteristics similar to'those shown in FIG. 4 when using a fourbarrel carburetor 10 as shown in FIGS. 1 and 2'and having the air fuelratio versus vacuum characteristics similar to those shown in FIG. 3.The upper limit of fuel economy for each vacuum level shown was obtainedby allowing the bleed valve 84 to be closed in the fourth gear inaccordance with the present invention and the lower limit was obtainedby preventing such closure in the fourth gear as by disconnectingconductor 88.

Having described one embodiment of the present invention, it isunderstood that the specific terms and examples are employed in adescriptive sense only and not for the purposes of limitation. Otherembodiments of the present invention, modifications thereof andalternatives thereto may be used. I therefore aim in the appended claimsto cover such modifications and changes as fall within the true spiritand scope of my invention.

What is claimed is:

1. In combination with an internal combustion engine providing a sourceof variable engine vacuum and a carburetor providing an air fuel mixtureto said engine:

a. fuel metering valve means operable to normally increasingly enrichthe fuel flow to said engine as said variable engine vacuum decreasesbelow a first predetermined vacuum level; and

b. vacuum control means responsive to a signal indicating vehicle speedand including energizable solenoid valve means and transmissioncontrolled switch means for energizing said solenoid valve means, saidtransmission controlled switch means having a first condition forcausing said solenoid valve means to normally allow said metering valvemeans to normally enrich said fuel flow and second condition for causingsaid solenoid valve means to delay said fuel metering valve means fromenriching fuel flow until said engine vacuum decreases below a secondpredetermined vacuum level less than said first predetermined level.

2. In combination with an internal combustion engine providing a sourceof variable engine vacuum and a carburetor for providing an air fuelmixture to said engine:

a. a vacuum unit for advancing the timing of ignition in said enginewhen said vacuum is communicated to said vacuum unit;

b. fuel metering valve means operable to normally increasingly enrichthe fuel flow to said engine as said variable engine vacuum decreasesbelow a first predetermined vacuum level;

c. solenoid valve means operable to normally allow said metering valvemeans to normally enrich said fuel flow and to otherwise prevent saidfuel metering valve means from enriching said fuel flow until saidengine vacuum decreases below a second predetermined vacuum level lessthan said first level; and control means responsive to a signalindicating vehicle speed for controlling said solenoid valve means andsaid vacuum advance unit and having a first condition operable tonormally prevent said vacuum from being communicated to said vacuum unitwhile also causing said solenoid means to normally allow said meteringvalve means to normally enrich said fuelfiow and having a secondcondition for permitting said vacuum to be communicated to said vacuumunit while also causing said solenoid to prevent said fuel meteringvalve means from enriching said fuel flow until said engine vacuumdecreases below a second predetermined vacuum level less than said firstpredetermined level.

3. In combination with an internal combustion engine for providing asource of variable engine vacuum signals and a carburetor for providingan air .fuel mixture to said engine:

a. a transmission with an input connected to said engine and an outputconnected to a load, said transmission having variable drive ratio meansfor varying the ratio of the speed of the output to the speed of theinput from a high drive ratio to a lower drive ratio;

b. fuel metering valve means operable to normally increasingly enrichthe fuel flow to said engine as said engine vacuums decrease below afirst predetermined vacuum level, said fuel metering valve meansnormally enriching said fuel flow by providing a flow area increasingfrom a minimum to a maximum flow area as said vacuum decreases belowsaid first level;

0. solenoid valve means operable to normally allow said fuel meteringvalve means to normally enrich said fuel flow and to otherwise preventsaid fuel metering valve means from providing a flow area between saidminimum and maximum flow areas until said engine vacuums decrease belowa second predetermined vacuum level less than said first level; and

said fuel metering valve means from increasing said flow area betweensaid minimum and maximum flow areas until said engine vacuums decreasebelow said second predetermined level.

1. In combination with an internal combustion engine providing a source of variable engine vacuum and a carburetor providing an air fuel mixture to said engine: a. fuel metering valve means operable to normally increasingly enrich the fuel flow to said engine as said variable engine vacuum decreases below a first predetermined vacuum level; and b. vacuum control means responsive to a signal indicating vehicle speed and including energizable solenoid valve means and transmission controlled switch means for energizing said solenoid valve means, said transmission controlled switch means having a first condition for causing said solenoid valve means to normally allow said metering valve means to normally enrich said fuel flow and second condition for causing said solenoid valve means to delay said fuel metering valve means from enriching fuel flow until said engine vacuum decreases below a second predetermined vacuum level less than said first predetermined level.
 2. In combination with an internal combustion engine providing a source of variable engine vacuum and a carburetor for providing an air fuel mixture to said engine: a. a vacuum unit for advancing the timing of ignition in said engine when said vacuum is communicated to said vacuum unit; b. fuel metering valve means operable to normally increasingly enrich the fuel flow to said engine as said variable engine vacuum decreases below a first predetermined vacuum level; c. solenoid valve means operable to normally allow said metering valve means to normally enrich said fuel flow and to otherwise prevent said fuel metering valve means from enriching said fuel flow until said engine vacuum decreases below a second predetermined vacuum level less than said first level; and d. control means responsive to a signal indicating vehicle speed for controlling said solenoid valve means and said vacuum advance unit and having a first condition operable to normally prevent said vacuum from being communicated to said vacuum unit while also causing said solenoid means to normally allow said metering valve means to normally enrich said fuel flow and having a second condition for permitting said vacuum to be communicated to said vacuum unit while also causing said solenoid to prevent said fuel metering valve means from enriching said fuel flow until said engine vacuum decreases below a second predetermined vacuum level less than said first predetermined level.
 3. In combination with an internal combustion engine for providing a source of variable engine vacuum signals and a carburetor for providing an air fuel mixture to said engine: a. a transmission with an input connected to said engine and an output connected to a load, said transmission having variable drive ratio means for varying the ratio of the speed of the output to the speed of the input from a high drive ratio to a lower drive ratio; b. fuel metering valve means operable to normally increasingly enrich the fuel flow to said engine as said engine vacuums decrease below a first predetermined vacuum level, said fuel metering valve means normally enriching said fuel flow by providing a flow area increasing from a minimum to a maximum flow area as said vacuum decreases below said first level; c. solenoid valve means operable to normally allow said fuel metering valve means to normally enrich said fuel flow and to otherwise prevent said fuel metering valve means from providing a flow area between said minimum and maximum flow areas until said engine vacuums decrease below a second predetermined vacuum level less than said first level; and d. transmission controlled switch means having a first condition for causing said solenoid valve means to normally allow said fuel metering valve means to normally enrich said fuel flow and a second condition when said transmission is in said high drive ratio to cause said solenoid valve means to prevent said fuel metering valve means from increasing said flow area between said minimum and maximum flow areas until said engine vacuums decrease below said second predetermined level. 